What is Seas?
Seas meaning The combination of both wind waves and swell. Used to describe the combination or interaction of wind waves and swell in which the separate components are not distinguished. This includes the case when swell is negligible or is not considered in describing sea state. Specifically, Seas2 = S2+W2 where S is the height of the swell and W is the height of the wind wave. When used, Seas should be considered as being the same as the Significant Wave Height
reference: National Weather Service Glossary